Fix doc example: space missing between concatenated strings
minor #1290 [Docs] Fix example: space missing between concatenated strings (GromNaN)

This PR was merged into the 1.15-dev branch.

Discussion
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[Docs] Fix example: space missing between concatenated strings

The expression `'Hello'~'Fabien'` produces `'HelloFabien'`, not `'Hello Fabien'`. I've just added a space after `'Hello'`.

Commits
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d6e0357 Fix doc example: space missing between concatenated strings